This article is a part of a very ambitious project, challenging the genetic way of determining the composition of a mixture of known and unknown microorganisms. Instead of studying microbialderived genetic fingerprints the authors are studying lipid fingerprints in human fecal samples. Based upon an assumption that certain lipids are unique to certain species, the authors used gas chromatography- mass spectrometry technology for a qualitative and quantitative evaluation of lipids present in feces.